EP0312552B1 - Device for eliminating parasitic rotations of mobile mirrors in laser gyrometers - Google Patents

Device for eliminating parasitic rotations of mobile mirrors in laser gyrometers Download PDF

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Publication number
EP0312552B1
EP0312552B1 EP19880901867 EP88901867A EP0312552B1 EP 0312552 B1 EP0312552 B1 EP 0312552B1 EP 19880901867 EP19880901867 EP 19880901867 EP 88901867 A EP88901867 A EP 88901867A EP 0312552 B1 EP0312552 B1 EP 0312552B1
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Prior art keywords
piezoelectric
voltage
ceramics
accelerations
amplifier
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EP19880901867
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German (de)
French (fr)
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EP0312552A1 (en
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Bernard Lucien Charles De Salaberry
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
    • G01C19/58—Turn-sensitive devices without moving masses
    • G01C19/64—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams
    • G01C19/66—Ring laser gyrometers
    • G01C19/661—Ring laser gyrometers details
    • G01C19/665—Ring laser gyrometers details control of the cavity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
    • G01C19/58—Turn-sensitive devices without moving masses
    • G01C19/64—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams
    • G01C19/66—Ring laser gyrometers
    • G01C19/661—Ring laser gyrometers details
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
    • G01C19/58—Turn-sensitive devices without moving masses
    • G01C19/64—Gyrometers using the Sagnac effect, i.e. rotation-induced shifts between counter-rotating electromagnetic beams
    • G01C19/66—Ring laser gyrometers
    • G01C19/68—Lock-in prevention
    • G01C19/70—Lock-in prevention by mechanical means

Definitions

  • the present invention relates to a device intended to suppress parasitic rotations of the mobile mirror (s) of laser gyrometers, under the effect of accelerations, mechanical activation or certain vibrations.
  • This invention applies to all triangular or square, single-axis or multi-axis laser gyros. It can also be applied to any laser provided with a cavity length servo by movable mirror.
  • the block of the gyrolaser is generally driven by an alternating angular movement of small amplitude, around an axis generally perpendicular to the plane of the optical cavity and which can be the axis of symmetry of the optical unit.
  • the frequency of the reciprocating movement is chosen so that the angular speed of the optical unit is most of the time outside the blind zone.
  • This movement is created by an oscillating device consisting of an elastic assembly generally placed inside and in the center of the optical unit.
  • the inertia of the block determines, with the stiffness of the elastic assembly, an oscillation frequency which will be maintained by a piezoelectric or electromagnetic motor system, controlled by an adequate electronic circuit.
  • This oscillation movement also called activation, causes accelerations on the different parts of the optical unit. These accelerations are all the more important as the point considered is distant from the axis of the device and the frequency chosen for activation is high.
  • the optical unit itself is not very sensitive to the deformations that could result from these accelerations. It is not the same for certain peripheral elements such as movable mirrors which are used to adjust the length of cavity. These mirrors are also called piezoelectric mirrors because they are generally moved by a set of piezoelectric ceramics.
  • these piezoelectric mirrors can deform and in particular rotate around an axis parallel to the activation axis. This rotation, although very low, affects the performance of gyrolasers.
  • the object of the present invention according to claim 1 is to completely suppress the parasitic rotations of the movable mirrors due to the deformations of the piezoelectric mirror assembly under the effect of accelerations by correcting them by piezoelectric means capable of creating an equal and opposite deformation. to the initial deformation, and controlled by an electric voltage coming from the activation system, electric voltage proportional to the accelerations undergone by said movable mirror assembly.
  • the laser gyrometer consists of an optical unit 1, mounted oscillating around an axis 16, thanks to a system of elastic blades 8 excited by piezoelectric ceramics 9.
  • a triangular or square optical path is hollowed out in the block and filled with a mixture of helium and neon excited by an electric current passing between one or more cathodes 4 and one or more anodes 5.
  • the path is closed by mirrors 2 and one or more movable mirrors 10, driven by one or more piezoelectric motors 11.
  • a movable mirror 10 and a piezoelectric motor 11 constitute the piezoelectric mirror assembly, of which many variants may exist.
  • An information output system is placed on one of the mirrors 2 and generally consists of at least one mixing prism 6 and a set of photoelectric cells 7 capable of detecting the movement of the interference fringes and, if necessary, the light intensity of the laser waves.
  • FIG. 3 shows, by exaggerating it, the deformation which occurs and the parasitic rotation of the mirror.
  • the peak amplitude of the activation movement is ⁇ .
  • the inertial force 19 drives the parts of the piezoelectric mirror in the direction of arrow 19.
  • the outer part 12 is deformed as shown in Figure 3.
  • the membranes 14 are also deformed as shown in the figure and the assembly rotates the central part 13 which will form an angle ⁇ with its initial position.
  • This angle ⁇ which varies in synchronism with the activation, can be very troublesome for the performance of the laser gyro.
  • the accelerations of which act in a direction situated in the plane of the laser gyro it undergoes other accelerations which also tend to deform the piezoelectric mirror.
  • the optical unit 1 assembly, activation mechanism 8 and base 25 not being infinitely stiff, it may have a resonance under the effect of the vibrations applied to the base of the laser gyro and parallel to it.
  • the arrow 20 in FIG. 4 presents this resonance movement, around a center of rotation 21 whose position depends on the geometry of the parts, under the effect of the excitation in vibration 22.
  • This resonance produces, at the level of the piezoelectric assembly, an alternative acceleration 23 of which one of the components 24 tends to deform the piezoelectric mirror and to misalign the optical cavity as will be understood by those skilled in the art.
  • the other accelerations that the gyrolaser can undergo and which can deform the piezoelectric mirror assembly can come from the vibrations of the Inertial Measurement Unit (IMU) on which the gyrolaser is mounted or from the accelerations and vibrations imposed from the outside on said UMI
  • IMU Inertial Measurement Unit
  • These vibrations and accelerations having any directions may have components in the two directions of deformation of the piezoelectric mirror assembly and will also cause parasitic rotations which are very troublesome for the performance of the laser gyro.
  • FIG. 5 illustrates the principle of the present invention which tends to suppress the parasitic rotation ⁇ .
  • a piezoelectric or electromagnetic means 26 introduces a deformation of the outer parts 12 equal and opposite to the deformation due to accelerations. Said means being excited by a voltage from an electronic circuit.
  • the main accelerations causing deformations are those due to activation, this is why the electronic circuits will have as input voltage, a voltage coming from the activation system and representing the angular position of said system.
  • Other inputs to the electronic circuits may receive voltages representing the accelerations undergone by the laser gyro. These accelerations can be measured by the accelerometers of the U.M.I. on which the laser gyro is mounted. They can also be measured by piezoelectric accelerometers placed on the laser gyro itself to measure the resonance vibrations.
  • Figures 5 and 6 show a first embodiment of such a device or piezoelectric ceramics 26 are bonded on each side of the outer parts 12 of the piezoelectric mirror assembly. These ceramics are controlled by voltages in phase opposition so that one contracts while the other expands, forcing the outer part 12 to straighten. In this embodiment, the ceramics compensate for the deformations in the plane of the laser gyro and therefore in the plane of activation.
  • these may be of semi-cylindrical shape, as shown in the sectional view of the FIG. 6.
  • These ceramics can also be planar 28 on the condition of producing on the external part 12 flats 27 on which they will be bonded, as shown in the section of FIG. 7.
  • the section of FIG. 8 shows an embodiment of the invention where 4 ceramics 29 and 30 arranged in pairs in the two vertical 29 and horizontal 30 directions make it possible to correct all the deformations brought by accelerations and vibrations to the mirror assembly piezoelectric.
  • the adaptation amplifier includes at least two inputs.
  • the input 36 receives a signal from a position detector 35 which can be one of the piezoelectric ceramics 9 placed on one of the blades 8 of the activation device or any other piezoresistive, electrostatic or even electromagnetic means as described in the French patent published under No. 2,562,239.
  • the second input 37 can receive a signal ⁇ 1 from the electronics for processing the accelerations measured by the accelerometers placed on the UMI, so that this signal ⁇ 1 does represent the acceleration undergone by the laser gyro in the same direction as that of the activation acceleration suba by the piezoelectric mirror assembly, which is perpendicular to the axis 50 of the movable mirror and located in the plane of the laser gyro perpendicular to its measurement axis 16.
  • the forces exerted by the ceramics 26 can be in phase with the acceleration due to the activation movement and straighten the piezoelectric mirror assembly. distorted by inertial forces.
  • FIG. 10 shows the control diagram of the device with 4 ceramics of FIG. 8.
  • the control circuits of the ceramics 30, acting in the horizontal plane are identical to those of FIG. 9. They therefore comprise an amplifier amplifier 39, a circuit gain and phase adjustment 32, a phase shift amplifier 33 and two voltage amplifiers 34.
  • the adapter amplifiers receive on their inputs 48 and 49, the voltage from the detector of the activation position 35 and the voltage ⁇ 1 representative of the acceleration undergone by the laser gyro in its plane and perpendicular to the axis 50 of the movable mirror.
  • the ceramic control circuits 29, acting in the vertical plane are similar to those of the horizontal channel. They therefore also include an adapter amplifier 39, a gain and phase adjustment circuit 32, a phase shift amplifier 33 and two voltage amplifiers 34. They also include a summing amplifier 47.
  • the input 38 of the adapter amplifier 39 receives a voltage representing the acceleration ⁇ 2, from the acceleration processing circuits, and which represents the acceleration undergone by the laser gyro in the direction of its
  • Another set of circuits 40 analogous to those which are generally used to adjust the length of the cavity, makes it possible to make a servo-control of the angular adjustment of the optical cavity, as those skilled in the art will readily understand.
  • This circuit preferably comprises an oscillator 41, a preamplifier 42, which receives, on its input 43, the light intensity information I L originating for example from photoelectric cells 7, a demodulator 44, a corrector network 45 and a summing amplifier 46 , whose output signal is sent to the ceramic control chain, on the summing amplifier 47.
  • FIG. 11 represents another embodiment of the invention, where the 4 ceramics 51 and 52 include external metallizations arranged in strips parallel to the axis 50 of the piezoelectric mirror, as shown in FIG. 12.
  • the central strip 53 is intended to measure the stresses undergone by ceramics when the piezoelectric mirror assembly deforms under the effect of accelerations and therefore measure the deformation of said assembly.
  • the lateral strips 54 are intended to receive the control voltages which, acting on the ceramics, will correct the deformations.
  • the control circuits are similar to the previous ones and constitute two control loops.
  • the signals from the central bands are sent to the differential inputs 55 of the adapter preamplifiers 56.
  • the amplified signals leave the voltage amplifiers 34 and are sent to the side bands 54 which are connected in parallel to each ceramic.
  • This device only provides compensation for alternative vibration accelerations. This is why the inputs 57 and 58 can receive the acceleration signals ⁇ 1 and ⁇ 2 as they were defined previously to compensate for the deformations due to continuous accelerations.
  • a device for controlling the angular alignment of the cavity 40 can also be used in this embodiment by bringing in its useful signal on the summing amplifier 59.
  • piezoelectric ceramics can be used, without departing from the scope of the invention, to correct the deformations of the piezoelectric mirror assemblies.
  • FIG. 13 shows an embodiment corresponding to this method.
  • the piezoelectric motor which creates the translational movement is produced using, for example, circular ceramics bonded to each side of an external membrane 69.
  • the face of each ceramic bonded to the membrane 69 has a unique metallization.
  • the other side has a metallization in 4 sectors, 61 to 64 for the exterior ceramic, 65 to 68 for the interior ceramic.
  • the polarizations of the two ceramics are carried out in opposite directions and the metallizations of the bonded faces are brought together at the cold point of the power supplies.
  • the metallizations 61 and 67, 63 and 65 are connected together, if two voltages of opposite signs are applied to them via the amplifiers 71 and if the membrane 69 is sufficiently thin, the parts of the ceramics placed under the metallizations 61 and 67 will, for example, expand and those, placed under the metallizations 63 and 65, will contract, forcing the central part 13 to rotate slightly, which will make it possible to compensate for the deformations of the external part 12 which will have occurred under the effect of accelerations parallel to the measurement axis 16 of the laser gyro.
  • the servo length control 69 is preferably performed according to a scheme well known to those skilled in the art. Its output signal 73 controls the eight metallizations via the 4 voltage amplifiers 71 and 72.
  • the horizontal correction channel identical to that of FIG. 10, receives on its inputs 49 and 48 the acceleration signals ⁇ 1 and the activation position signals from the detector 35.
  • the vertical correction channel also identical to that of FIG. 10, receives, on its input 38, the acceleration signal ⁇ 2 and, on the summing amplifier 47, the signal coming from the angular alignment control circuit of cavity 40.
  • the two cavity length servo-control circuits 62 and the angular adjustment servo-control circuit 40 receive on their inputs a voltage representing the light intensity I L , measured for example by photoelectric cells 7.

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  • Engineering & Computer Science (AREA)
  • Optics & Photonics (AREA)
  • Electromagnetism (AREA)
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Abstract

A device for eliminating parasitic rotations of the mobile mirrors (15) of gyrolasers driven by piezoelectric ceramics (11). These parasitic rotations are caused by deformations of the external part (12) which constitutes the body of the mobile mirror and is attached to the optical block (1) under the effect of the accelerations of the activating motion. These parasitic rotations are corrected in the invention by semi-circular ceramics (26) glued around the external part (12), which, when driven by an electronic circuit, correct the deformations of the said external part (12). The invention is applicable to all lasers and in particular to gyrolasers.

Description

La présente invention concerne un dispositif destiné à supprimer les rotations parasites du ou des miroirs mobiles des gyromètres à laser, sous l'effet des accélérations, de l'activation mécanique ou de certaines vibrations.The present invention relates to a device intended to suppress parasitic rotations of the mobile mirror (s) of laser gyrometers, under the effect of accelerations, mechanical activation or certain vibrations.

Cette invention s'applique à tous les gyromètres laser triangulaires ou carrés, monoaxes ou multiaxes. Elle peut également s'appliquer à tout laser muni d'un asservissement de longueur de cavité par miroir mobile.This invention applies to all triangular or square, single-axis or multi-axis laser gyros. It can also be applied to any laser provided with a cavity length servo by movable mirror.

Le principe de fonctionnement des gyromètres à laser est maintenant bien connu et l'homme de l'art n'aura aucune peine à suivre les explications qui vont suivre.The operating principle of laser gyros is now well known and those skilled in the art will have no trouble following the explanations which follow.

Les gyromètres à laser, appelés dans ce qui va suivre gyrolasers, sont généralement constitués (V. WO-A-8 601 887):

  • d'un parcours optique triangulaire ou carré, creusé dans un bloc de matériau isolant et à faible coefficient de dilatation (figure 1). Ledit parcours optique étant délimité par trois ou quatre miroirs et fixés sur le bloc.
  • d'un milieu amplificateur, permettant de générer dans la cavité optique deux ondes lumineuses tournant l'une dans un sens et l'autre dans l'autre. Les interférences entre ces deux ondes vont permettre la mesure de la rotation du gyromètre autour d'un axe perpendiculaire au plan de la cavité optique.
  • d'un dispositif de mélange des ondes lumineuses pour créer des franges d'interférence sur un ensemble de cellules photoélectriques. Le défilement desdites franges représentant la rotation angulaire du gyrolaser, sera transformé par lesdites cellules photoélectriques en signaux électriques utilisables.
  • d'un dispositif de mesure de l'intensité lumineuse des ondes laser.
Laser gyros, called in what follows gyrolasers, are generally made up (V. WO-A-8 601 887):
  • a triangular or square optical path, hollowed out in a block of insulating material and with a low coefficient of expansion (Figure 1). Said optical path being delimited by three or four mirrors and fixed on the block.
  • an amplifying medium, making it possible to generate in the optical cavity two light waves rotating one in one direction and the other in the other. The interference between these two waves will allow the measurement of the rotation of the gyrometer around an axis perpendicular to the plane of the optical cavity.
  • a device for mixing light waves to create interference fringes on a set of photoelectric cells. The scrolling of said fringes representing the angular rotation of the laser gyro, will be transformed by said photoelectric cells into usable electrical signals.
  • a device for measuring the light intensity of laser waves.

Pour éviter les effets du phénomène bien connu de blocage entre les deux ondes lumineuses circulant dans le parcours optique (zone aveugle), le bloc du gyrolaser est généralement animé d'un mouvement angulaire alternatif de faible amplitude, autour d'un axe généralement perpendiculaire au plan de la cavité optique et qui peut être l'axe de symétrie du bloc optique. La fréquence du mouvement alternatif est choisie de telle façon que la vitesse angulaire du bloc optique soit la plus grande partie du temps en dehors de la zone aveugle.To avoid the effects of the well-known blocking phenomenon between the two light waves circulating in the optical path (blind zone), the block of the gyrolaser is generally driven by an alternating angular movement of small amplitude, around an axis generally perpendicular to the plane of the optical cavity and which can be the axis of symmetry of the optical unit. The frequency of the reciprocating movement is chosen so that the angular speed of the optical unit is most of the time outside the blind zone.

Ce mouvement est créé par un dispositif oscillant constitué d'un ensemble élastique généralement placé à l'intérieur et au centre du bloc optique. L'inertie du bloc détermine, avec la raideur de l'ensemble élastique une fréquence d'oscillation qui sera entretenue par un système de moteur piézoélectrique ou électromagnétique, commandé par un circuit électronique adéquat.This movement is created by an oscillating device consisting of an elastic assembly generally placed inside and in the center of the optical unit. The inertia of the block determines, with the stiffness of the elastic assembly, an oscillation frequency which will be maintained by a piezoelectric or electromagnetic motor system, controlled by an adequate electronic circuit.

Ce mouvement d'oscillation, appelé encore activation, entraîne des accélérations sur les différentes parties du bloc optique. Ces accélérations sont d'autant plus importantes que le point considéré est éloigné de l'axe du dispositif et que la fréquence choisie pour l'activation est élevée.This oscillation movement, also called activation, causes accelerations on the different parts of the optical unit. These accelerations are all the more important as the point considered is distant from the axis of the device and the frequency chosen for activation is high.

Le bloc optique lui même est assez peu sensible aux déformations que pourraient entraîner ces accélérations. Il n'en est pas de même de certains éléments périphériques tels que les miroirs mobiles qui servent à ajuster la longueur de cavité. Ces miroirs sont encore appelés miroirs piézoélectriques parce qu'ils sont généralement mus par un ensemble de céramiques piézoélectriques.The optical unit itself is not very sensitive to the deformations that could result from these accelerations. It is not the same for certain peripheral elements such as movable mirrors which are used to adjust the length of cavity. These mirrors are also called piezoelectric mirrors because they are generally moved by a set of piezoelectric ceramics.

Sous l'effet des accélérations alternatives d'activation qui sont bien entendu tangentes aux mouvements de chaque points, ou de toute autre accélération, ces miroirs piézoélectriques peuvent se déformer et notamment tourner autour d'un axe parallèle à l'axe d'activation. Cette rotation, bien que très faible, nuit aux performances des gyrolasers.Under the effect of alternative activation accelerations which are of course tangent to the movements of each point, or any other acceleration, these piezoelectric mirrors can deform and in particular rotate around an axis parallel to the activation axis. This rotation, although very low, affects the performance of gyrolasers.

Par une conception bien adaptée du miroir piézoélectrique, il peut être possible de diminuer ces rotations parasites, mais il est très difficile de les éliminer complètement.By a well-adapted design of the piezoelectric mirror, it may be possible to reduce these parasitic rotations, but it is very difficult to eliminate them completely.

La présente invention selon la revendication 1 a pour objet de supprimer complètement les rotations parasites des miroirs mobiles dues aux déformations de l'ensemble miroir piézoélectrique sous l'effet des accélérations en les corrigeant par un moyen piézoélectrique, capable de créer une déformation égale et opposée à la déformation initiale, et commandé par une tension électrique issue du système d'activation, tension électrique proportionnelle aux accélérations subies par ledit ensemble miroir mobile.The object of the present invention according to claim 1 is to completely suppress the parasitic rotations of the movable mirrors due to the deformations of the piezoelectric mirror assembly under the effect of accelerations by correcting them by piezoelectric means capable of creating an equal and opposite deformation. to the initial deformation, and controlled by an electric voltage coming from the activation system, electric voltage proportional to the accelerations undergone by said movable mirror assembly.

L'invention sera mieux comprise et d'autres avantages de l'invention apparaîtront à l'aide de la description qui suit, en référence aux figures annexées.

  • La figure 1, rappelle le principe de réalisation d'un gyrolaser typique.
  • La figure 2 montre, en vue de dessus, la direction des différentes forces agissant sur le ou les miroirs piézoélectriques et dues aux mouvements d'activation.
  • La figure 3 montre la déformation et la rotation parasite du miroir piézoélectrique sous l'effet des accélérations de l'activation.
  • La figure 4 présente un mode de résonnance du gyrolaser susceptible d'entraîner des déformations de l'ensemble piézoélectrique.
  • La figure 5 montre un premier mode de réalisation de l'invention ou les déformations du miroir piézoélectrique sont supprimées en utilisant d'autres céramiques piézoélectriques commandées par un système électronique.
  • La figure 6 est une vue en coupe perpendiculaire à l'axe du miroir mobile et qui montre la disposition des céramiques semi-cylindriques.
  • La figure 7 est également une vue en coupe du même dispositif équipé de céramiques plates.
  • La figure 8 est une vue en coupe du dispositif équipé de deux paires de céramiques agissant dans deux directions.
  • La figure 9 montre le schéma de principe de la commande électrique utilisée pour le dispositif de la figure 4.
  • La figure 10 montre le schéma de principe de la commande électrique utilisée pour le dispositif à deux paires de céramiques.
  • La figure 11 est une vue en coupe du dispositif où des électrodes supplémentaires placées sur les céramiques permettent de mesurer les déformations de l'ensemble mobile piézoélectrique et de les corriger par asservissement. Cette figure présente également le schéma de commande utilisé.
  • La figure 12 montre une disposition particulière d'électrodes sur une des céramiques utilisée dans la réalisation de la figure 11.
  • La figure 13 montre un autre mode de réalisation de l'invention où la correction de déformation et l'asservissement de longueur de cavité sont réalisés avec le même ensemle de céramiques.
The invention will be better understood and other advantages of the invention will become apparent from the following description, with reference to the appended figures.
  • Figure 1 recalls the principle of making a typical laser gyro.
  • Figure 2 shows, in top view, the direction of the different forces acting on the piezoelectric mirror (s) and due to the activation movements.
  • FIG. 3 shows the distortion and the parasitic rotation of the piezoelectric mirror under the effect of the acceleration of the activation.
  • FIG. 4 shows a mode of resonance of the laser gyro capable of causing deformations of the piezoelectric assembly.
  • FIG. 5 shows a first embodiment of the invention in which the deformations of the piezoelectric mirror are eliminated by using other piezoelectric ceramics controlled by an electronic system.
  • Figure 6 is a sectional view perpendicular to the axis of the movable mirror and which shows the arrangement of semi-cylindrical ceramics.
  • Figure 7 is also a sectional view of the same device equipped with flat ceramics.
  • Figure 8 is a sectional view of the device equipped with two pairs of ceramics acting in two directions.
  • Figure 9 shows the block diagram of the electrical control used for the device of Figure 4.
  • Figure 10 shows the block diagram of the electrical control used for the device with two pairs of ceramics.
  • FIG. 11 is a sectional view of the device where additional electrodes placed on the ceramics make it possible to measure the deformations of the piezoelectric mobile assembly and to correct them by slaving. This figure also shows the control diagram used.
  • FIG. 12 shows a particular arrangement of electrodes on one of the ceramics used in the embodiment of FIG. 11.
  • FIG. 13 shows another embodiment of the invention in which the correction of deformation and the control of the length of cavity are carried out with the same set of ceramics.

Tel qu'il est représenté sur la figure 1, le gyromètre laser est constitué d'un bloc optique 1, monté oscillant autour d'un axe 16, grâce à un système de lames élastiques 8 excitées par des céramiques piézoélectriques 9.As shown in FIG. 1, the laser gyrometer consists of an optical unit 1, mounted oscillating around an axis 16, thanks to a system of elastic blades 8 excited by piezoelectric ceramics 9.

Un parcours optique triangulaire ou carré est creusé dans le bloc et rempli d'un mélange d'hélium et de néon excité par un courant électrique passant entre une ou plusieurs cathodes 4 et une ou plusieurs anodes 5.A triangular or square optical path is hollowed out in the block and filled with a mixture of helium and neon excited by an electric current passing between one or more cathodes 4 and one or more anodes 5.

Le parcours est fermé par des miroirs 2 et un ou plusieurs miroirs mobiles 10, mus par un ou plusieurs moteurs piézoélectriques 11. Un miroir mobile 10 et un moteur piézoélectrique 11 constituent l'ensemble miroir piézoélectrique dont de nombreuses variantes peuvent exister.The path is closed by mirrors 2 and one or more movable mirrors 10, driven by one or more piezoelectric motors 11. A movable mirror 10 and a piezoelectric motor 11 constitute the piezoelectric mirror assembly, of which many variants may exist.

Un système de sortie des informations est placé sur l'un des miroirs 2 et est généralement constitué d'au moins un prisme de mélange 6 et d'un ensemble de cellules photoélectriques 7 capables de détecter le défilement des franges d'interférences et, si nécessaire, l'intensité lumineuse des ondes laser.An information output system is placed on one of the mirrors 2 and generally consists of at least one mixing prism 6 and a set of photoelectric cells 7 capable of detecting the movement of the interference fringes and, if necessary, the light intensity of the laser waves.

La figure 2 représente une partie du bloc optique 1 du gyrolaser et le miroir piézoélectrique. Celui-ci est généralement constitué:

  • d'une partie fixe extérieure 12, généralement cylindrique, mais qui pourrait prendre toute autre forme en restant dans le cadre de l'invention.
  • d'une partie mobile intérieure 13 maintenue dans la partie fixe par une ou plusieurs membranes fines 14 qui lui permettent de se déplacer suivant son axe de quelques microns. Cette partie mobile porte à son extrémité, située du coté du bloc optique, une partie réfléchissante 15 constituant le miroir proprement dit.
  • d'un moteur piézoélectrique pour lequel il existe de très nombreuses solution de réalisation. L'une des solutions couramment adoptée consiste à utiliser un bilame piézoélectrique 11 fixé par un ensemble de pièces métalliques sur la partie extérieure 12 déjà décrite.
FIG. 2 represents a part of the optical unit 1 of the gyrolaser and the piezoelectric mirror. This generally consists of:
  • an outer fixed part 12, generally cylindrical, but which could take any other form while remaining within the scope of the invention.
  • an inner movable part 13 held in the fixed part by one or more thin membranes 14 which allow it to move along its axis by a few microns. This movable part carries at its end, located on the side of the optical unit, a reflecting part 15 constituting the mirror itself.
  • of a piezoelectric motor for which there are very many implementation solutions. One of the commonly adopted solutions consists in using a piezoelectric bimetallic strip 11 fixed by a set of metal parts on the external part 12 already described.

L'ensemble de ces pièces présente une inertie qui s'oppose à l'accélération alternative de l'activation. L'axe de l'activation étant en 16, l'accélération alternative est figurée par les flèches 17. Du fait que l'accélération d'activation 17 est en opposition de phase avec le déplacement angulaire 18 de ladite activation, la force d'inertie 19 opposée à l'accélération, sera, elle, en phase avec ledit déplacement. La pièce extérieure 12 n'étant pas infiniment rigide aura tendance à se déformer alternativement et dans le même sens 18 que le déplacement du bloc optique 1.All of these parts have an inertia which opposes the alternative acceleration of activation. The axis of the activation being at 16, the alternative acceleration is represented by the arrows 17. Because the activation acceleration 17 is in phase opposition with the angular displacement 18 of said activation, the force of inertia 19 opposite the acceleration will be in phase with said displacement. The external part 12 not being infinitely rigid will tend to deform alternately and in the same direction 18 as the displacement of the optical unit 1.

La figure 3 montre, en l'exagérant, la déformation qui se produit et la rotation parasite du miroir.Figure 3 shows, by exaggerating it, the deformation which occurs and the parasitic rotation of the mirror.

L'amplitude crête du mouvement d'activation est α. Lorsque le bloc optique est déplacé d'un angle α par le mouvement d'activation, l'accélération subie par le bloc et donc par le miroir piézoélectrique est maximum et dirigée suivant la flèche 17. La force d'inertie 19 entraîne les pièces du miroir piézoélectrique dans le sens de la flèche 19.The peak amplitude of the activation movement is α. When the optical unit is moved by an angle α by the activation movement, the acceleration undergone by the unit and therefore by the piezoelectric mirror is maximum and directed along arrow 17. The inertial force 19 drives the parts of the piezoelectric mirror in the direction of arrow 19.

La pièce extérieure 12 se déforme comme l'indique la figure 3. Les membranes 14 se déforment également comme l'indique la figure et l'ensemble entraîne en rotation la partie centrale 13 qui fera un angle β avec sa position initiale.The outer part 12 is deformed as shown in Figure 3. The membranes 14 are also deformed as shown in the figure and the assembly rotates the central part 13 which will form an angle β with its initial position.

Cet angle β, qui varie en synchronisme avec l'activation, peut être très gênant pour les performances du gyrolaser.This angle β, which varies in synchronism with the activation, can be very troublesome for the performance of the laser gyro.

Outre l'activation dont les accélérations agissent dans une direction située dans le plan du gyrolaser, celui-ci subit d'autres accélérations qui tendent, elles, aussi à déformer le miroir piézoélectrique.In addition to the activation, the accelerations of which act in a direction situated in the plane of the laser gyro, it undergoes other accelerations which also tend to deform the piezoelectric mirror.

Tout d'abord, l'ensemble bloc optique 1, mécanisme d'activation 8 et socle 25 n'étant pas infiniment raide, il peut présenter une résonnance sous l'effet des vibrations appliquées au socle du gyrolaser et parallèlement à celui-ci.First of all, the optical unit 1 assembly, activation mechanism 8 and base 25 not being infinitely stiff, it may have a resonance under the effect of the vibrations applied to the base of the laser gyro and parallel to it.

La flèche 20 sur la figure 4 présente ce mouvement de résonnance, autour d'un centre de rotation 21 dont la position dépend de la géométrie des pièces, sous l'effet de l'excitation en vibration 22.The arrow 20 in FIG. 4 presents this resonance movement, around a center of rotation 21 whose position depends on the geometry of the parts, under the effect of the excitation in vibration 22.

Cette résonnance produit, au niveau de l'ensemble piézoélectrique, une accélération alternative 23 dont l'une des composantes 24 tend à déformer le miroir piézoélectrique et à désaligner la cavité optique ainsi que l'homme de l'art le comprendra aisément.This resonance produces, at the level of the piezoelectric assembly, an alternative acceleration 23 of which one of the components 24 tends to deform the piezoelectric mirror and to misalign the optical cavity as will be understood by those skilled in the art.

Les autres accélérations que peut subir le gyrolaser et qui peuvent déformer l'ensemble miroir piézoélectrique peuvent provenir des vibrations de l'Unité de Mesure Inertielle (U.M.I.) sur laquelle le gyrolaser est monté ou des accélérations et vibrations imposées de l'extérieur à ladite U.M.I. Ces vibrations et accélérations ayant des directions quelconques pourront avoir des composantes dans les deux directions de déformation de l'ensemble miroir piézoélectrique et entraîneront également des rotations parasites très gênantes pour les performances du gyrolaser.The other accelerations that the gyrolaser can undergo and which can deform the piezoelectric mirror assembly can come from the vibrations of the Inertial Measurement Unit (IMU) on which the gyrolaser is mounted or from the accelerations and vibrations imposed from the outside on said UMI These vibrations and accelerations having any directions may have components in the two directions of deformation of the piezoelectric mirror assembly and will also cause parasitic rotations which are very troublesome for the performance of the laser gyro.

La figure 5 illustre le principe de la présente invention qui tend à supprimer la rotation parasite β.FIG. 5 illustrates the principle of the present invention which tends to suppress the parasitic rotation β.

A cet effet, un moyen piézoélectriçue 26 ou électromagnétique introduit une déformation des pièces extérieures 12 égale et opposée à la déformation due aux accélérations. Ledit moyen étant excité par une tension issue d'un circuit électronique.To this end, a piezoelectric or electromagnetic means 26 introduces a deformation of the outer parts 12 equal and opposite to the deformation due to accelerations. Said means being excited by a voltage from an electronic circuit.

Comme il a été dit ci-dessus, les principales accélérations entraînant des déformations sont celles dues à l'activation, c'est pourquoi les circuits électroniques auront comme tension d'entrée, une tension issue du système d'activation et représentant la position angulaire dudit système.As it was said above, the main accelerations causing deformations are those due to activation, this is why the electronic circuits will have as input voltage, a voltage coming from the activation system and representing the angular position of said system.

D'autres entrées des circuits électroniques pourront recevoir des tensions représentant les accélérations subies par le gyrolaser. Ces accélérations peuvent être mesurées par les accéléromètres de l'U.M.I. sur laquelle le gyrolaser est monté. Elles peuvent aussi être mesurées par des accéléromètres piézoélectriques placés sur le gyrolaser lui-même pour mesurer les vibrations de résonnance.Other inputs to the electronic circuits may receive voltages representing the accelerations undergone by the laser gyro. These accelerations can be measured by the accelerometers of the U.M.I. on which the laser gyro is mounted. They can also be measured by piezoelectric accelerometers placed on the laser gyro itself to measure the resonance vibrations.

Les figures 5 et 6 montrent une première réalisation d'un tel dispositif ou des céramiques piézoélectriques 26 sont collées de chaque côté des parties extérieures 12 de l'ensemble miroir piézoélectrique. Ces céramiques sont commandées par des tensions en opposition de phase de telle sorte que l'une se contracte pendant que l'autre se dilate, obligeant la partie extérieure 12 à se redresser. Dans cette réalisation, les céramiques viennent compenser les déformations dans le plan du gyrolaser et donc dans le plan de l'activation.Figures 5 and 6 show a first embodiment of such a device or piezoelectric ceramics 26 are bonded on each side of the outer parts 12 of the piezoelectric mirror assembly. These ceramics are controlled by voltages in phase opposition so that one contracts while the other expands, forcing the outer part 12 to straighten. In this embodiment, the ceramics compensate for the deformations in the plane of the laser gyro and therefore in the plane of activation.

Pour assurer une meilleure liaison entre la partie extérieure 12 et les céramiques 26, celles-ci peuvent être de forme semi-cylindrique, comme le montre la vue en coupe de la figure 6. Ces céramiques peuvent également être planes 28 à condition de réaliser sur la partie extérieure 12 des méplats 27 sur lesquelles elles seront collées, comme le montre la coupe de la figure 7.To ensure a better connection between the outer part 12 and the ceramics 26, these may be of semi-cylindrical shape, as shown in the sectional view of the FIG. 6. These ceramics can also be planar 28 on the condition of producing on the external part 12 flats 27 on which they will be bonded, as shown in the section of FIG. 7.

La coupe de la figure 8 montre un mode de réalisation de l'invention ou 4 céramiques 29 et 30 disposées par paire dans les deux directions verticales 29 et horizontales 30 permettent de corriger toutes les déformations apportées par les accélérations et vibrations à l'ensemble miroir piézoélectrique.The section of FIG. 8 shows an embodiment of the invention where 4 ceramics 29 and 30 arranged in pairs in the two vertical 29 and horizontal 30 directions make it possible to correct all the deformations brought by accelerations and vibrations to the mirror assembly piezoelectric.

La figure 9 montre le schéma du circuit de commande du dispositif correcteur de la figure 5. Ce circuit, dans un de ses modes de réalisation préférés, comprend:

  • Un amplificateur d'adaptation 31,
  • Un circuit de réglage de gain et de phase 32,
  • Un amplificateur inverseur 33,
  • Deux amplificateurs de tension 34 qui commandent les céramiques piézoélectriques.
FIG. 9 shows the diagram of the control circuit of the correction device of FIG. 5. This circuit, in one of its preferred embodiments, comprises:
  • An adaptation amplifier 31,
  • A gain and phase adjustment circuit 32,
  • An inverting amplifier 33,
  • Two voltage amplifiers 34 which control the piezoelectric ceramics.

L'amplificateur d'adaptation comprend au moins deux entrées. L'entrée 36 reçoit un signal issu d'un détecteur de position 35 qui peut être une des céramiques piézoélectriques 9 placées sur l'une des lames 8 du dispositif d'activation ou tout autre moyen piézorésistif, électrostatique ou encore électromagnétique tel que décrit dans le brevet Francais publié sous le n° 2.562.239.The adaptation amplifier includes at least two inputs. The input 36 receives a signal from a position detector 35 which can be one of the piezoelectric ceramics 9 placed on one of the blades 8 of the activation device or any other piezoresistive, electrostatic or even electromagnetic means as described in the French patent published under No. 2,562,239.

La deuxième entrée 37 peut recevoir un signal γ1 issu de l'électronique de traitement des accélérations mesurées par les accéléromètres placés sur l'U.M.I., de telle sorte que ce signal γ1 représente bien l'accélération subie par le gyrolaser dans la même direction que celle de l'accélération d'activation suba par l'ensemble miroir piézoélectrique, lesquelle est perpendiculaire à l'axe 50 du miroir mobile et située dans le plan du gyrolaser perpendiculaire à son axe de mesure 16.The second input 37 can receive a signal γ1 from the electronics for processing the accelerations measured by the accelerometers placed on the UMI, so that this signal γ1 does represent the acceleration undergone by the laser gyro in the same direction as that of the activation acceleration suba by the piezoelectric mirror assembly, which is perpendicular to the axis 50 of the movable mirror and located in the plane of the laser gyro perpendicular to its measurement axis 16.

Dans ces conditions, et après un réglage convenable du gain et de la phase, les forces exercées par les céramiques 26 peuvent être en phase avec l'accélération due au mouvement d'activation et redresser l'ensemble miroir piézoélectrique déformé par les forces d'inertie.Under these conditions, and after a suitable gain and phase adjustment, the forces exerted by the ceramics 26 can be in phase with the acceleration due to the activation movement and straighten the piezoelectric mirror assembly. distorted by inertial forces.

La figure 10 montre le schéma de commande du dispositif à 4 céramiques de la figure 8. Les circuits de commande des céramiques 30, agissant dans le plan horizontal sont identiques à ceux de la figure 9. Ils comportent donc un amplificateur adaptateur 39, un circuit de réglage de gain et de phase 32, un amplificateur déphaseur 33 et deux amplificateurs de tension 34. Les amplificateurs adaptateurs reçoivent sur leurs entrées 48 et 49, la tension issue du détecteur de la position d'activation 35 et la tension γ1 représentative de l'accélération subie par le gyrolaser dans son plan et perpendiculairement à l'axe 50 du miroir mobile. Les circuits de commande des céramiques 29, agissant dans le plan vertical, sont analogues à ceux de la voie horizontale. Ils comportent donc aussi un amplificateur adaptateur 39, un circuit de réglage de gain et de phase 32, un amplificateur déphaseur 33 et deux amplificateur de tension 34. Ils comportent en outre un amplificateur sommateur 47. L'entrée 38 de l'amplificateur adaptateur 39 reçoit une tension représentant l'accélération γ2, issue des circuits de traitement des accélérations, et qui représente l'accélération subie par le gyrolaser dans la direction de son axe de mesure 16.FIG. 10 shows the control diagram of the device with 4 ceramics of FIG. 8. The control circuits of the ceramics 30, acting in the horizontal plane are identical to those of FIG. 9. They therefore comprise an amplifier amplifier 39, a circuit gain and phase adjustment 32, a phase shift amplifier 33 and two voltage amplifiers 34. The adapter amplifiers receive on their inputs 48 and 49, the voltage from the detector of the activation position 35 and the voltage γ1 representative of the acceleration undergone by the laser gyro in its plane and perpendicular to the axis 50 of the movable mirror. The ceramic control circuits 29, acting in the vertical plane, are similar to those of the horizontal channel. They therefore also include an adapter amplifier 39, a gain and phase adjustment circuit 32, a phase shift amplifier 33 and two voltage amplifiers 34. They also include a summing amplifier 47. The input 38 of the adapter amplifier 39 receives a voltage representing the acceleration γ2, from the acceleration processing circuits, and which represents the acceleration undergone by the laser gyro in the direction of its measurement axis 16.

Un autre ensemble de circuits 40, analogues à ceux qui sont généralement utilisés pour ajuster la longueur de la cavité, permet de faire un asservissement du réglage angulaire de la cavité optique, ainsi que l'homme de l'art le comprendra aisément.Another set of circuits 40, analogous to those which are generally used to adjust the length of the cavity, makes it possible to make a servo-control of the angular adjustment of the optical cavity, as those skilled in the art will readily understand.

Ce circuit comprend préférentiellement un oscillateur 41, un préamplificateur 42, qui reçoit, sur son entrée 43, l'information d'intensité lumineuse IL issue par exemple des cellules photoélectriques 7, un démodulateur 44, un réseau correcteur 45 et un amplificateur sommateur 46, dont le signal de sortie est envoyé dans la chaîne de commande des céramiques, sur l'amplificateur sommateur 47.This circuit preferably comprises an oscillator 41, a preamplifier 42, which receives, on its input 43, the light intensity information I L originating for example from photoelectric cells 7, a demodulator 44, a corrector network 45 and a summing amplifier 46 , whose output signal is sent to the ceramic control chain, on the summing amplifier 47.

La figure 11 représente un autre mode de réalisation de l'invention, où les 4 céramiques 51 et 52, comportent des métallisations extérieures disposées en bandes paralllèles à l'axe 50 du miroir piézoélectrique, ainsi qu'elles sont représentées sur la figure 12. La bande centrale 53 est destinée à mesurer les contraintes subies par les céramiques lorsque l'ensemble miroir piézoélectrique se déforme sous l'effet des accélérations et donc à mesurer la déformation dudit ensemble. Les bandes latérales 54 sont destinées à recevoir les tensions de commande qui, agissait sur les céramiques, viendront corriger les déformations.FIG. 11 represents another embodiment of the invention, where the 4 ceramics 51 and 52 include external metallizations arranged in strips parallel to the axis 50 of the piezoelectric mirror, as shown in FIG. 12. The central strip 53 is intended to measure the stresses undergone by ceramics when the piezoelectric mirror assembly deforms under the effect of accelerations and therefore measure the deformation of said assembly. The lateral strips 54 are intended to receive the control voltages which, acting on the ceramics, will correct the deformations.

Les circuits de commande sont analogues aux précédents et constituent deux boucles d'asservissement. Les signaux issus des bandes centrales sont envoyés sur les entrées 55 différentielles des préamplificateurs adaptateurs 56. Les signaux amplifiés sortent des amplificateurs de tension 34 et sont envoyés aux bandes latérales 54 qui sont branchées en parallèle sur chaque céramique.The control circuits are similar to the previous ones and constitute two control loops. The signals from the central bands are sent to the differential inputs 55 of the adapter preamplifiers 56. The amplified signals leave the voltage amplifiers 34 and are sent to the side bands 54 which are connected in parallel to each ceramic.

A noter toutefois que des réseaux correcteurs particuliers 70 doivent être placés dans le circuits pour assurer la stabilité de ces asservissements.Note, however, that special correction networks 70 must be placed in the circuit to ensure the stability of these controls.

Ce dispositif n'assure qu'une compensation des accélérations alternatives de vibrations. C'est pourquoi les entrées 57 et 58 peuvent recevoir les signaux d'accélération γ1 et γ2 tels qu'ils ont été définis précédemment pour compenser les déformations dues aux accélérations continues.This device only provides compensation for alternative vibration accelerations. This is why the inputs 57 and 58 can receive the acceleration signals γ1 and γ2 as they were defined previously to compensate for the deformations due to continuous accelerations.

Un dispositif d'asservissement de l'alignement angulaire de la cavité 40, analogue à celui de la figure 10 déjà décrit, peut également être utilisé dans cette réalisation en faisant rentrer son signal utile sur l'amplificateur sommateur 59.A device for controlling the angular alignment of the cavity 40, similar to that of FIG. 10 already described, can also be used in this embodiment by bringing in its useful signal on the summing amplifier 59.

La disposition, la polarisation, la forme et le nombre des électrodes pourront bien entendu être modifiés sans sortir du cadre de l'invention.The arrangement, the polarization, the shape and the number of the electrodes can of course be modified without departing from the scope of the invention.

On pourra utiliser, sans sortir du cadre de l'invention, de nombreuses autres dispositions de céramiques piézoélectriques pour corriger les déformations des ensembles miroirs piézoélectriques.Many other arrangements of piezoelectric ceramics can be used, without departing from the scope of the invention, to correct the deformations of the piezoelectric mirror assemblies.

On pourra notamment utiliser les céramiques du moteur piézoélectrique lui-même pour créer à la fois le mouvement de translation de l'asservissement de longueur de cavité et le mouvement de rotation β′ du miroir égal et opposé à la rotation parasite β entraînée par les accélérations.We can in particular use the ceramics of the piezoelectric motor itself to create both the translational movement of the cavity length control and the rotational movement β ′ of the mirror equal and opposite to the β parasitic rotation caused by accelerations.

La figure 13 présente un mode de réalisation correspondant à cette méthode. Le moteur piézoélectrique qui crée le mouvement de translation est réalisé à l'aide par exemple de céramiques circulaires collées de chaque côté d'une membrane 69 externe. La face de chaque céramique, collée à la membrane 69 comporte une métallisation unique. l'autre face comporte une métallisation en 4 secteurs, 61 à 64 pour la céramique extérieure, 65 à 68 pour la céramique intérieure. Les polarisations des deux céramiques sont réalisées en sens opposés et les métallisations des faces collées sont réunies au point froid des alimentations.FIG. 13 shows an embodiment corresponding to this method. The piezoelectric motor which creates the translational movement is produced using, for example, circular ceramics bonded to each side of an external membrane 69. The face of each ceramic bonded to the membrane 69 has a unique metallization. the other side has a metallization in 4 sectors, 61 to 64 for the exterior ceramic, 65 to 68 for the interior ceramic. The polarizations of the two ceramics are carried out in opposite directions and the metallizations of the bonded faces are brought together at the cold point of the power supplies.

Si, par conséquent, on commande les huit secteurs par la même tension, issue des quatre amplificateurs 71 et 72, l'une des céramiques va se dilater et l'autre va se contracter, et ceci sur toute leur surface. L'effet bilame qui s'en suit déplacera le miroir mobile 10 le long de son axe 50 et permettra de réaliser l'asservissement de longueur de cavité.If, consequently, the eight sectors are controlled by the same voltage, coming from the four amplifiers 71 and 72, one of the ceramics will expand and the other will contract, and this over their entire surface. The bimetallic effect which follows will move the movable mirror 10 along its axis 50 and will make it possible to achieve the servo-control of cavity length.

Si l'on relie entre elles les métallisations 61 et 67, 63 et 65, si on leur applique par l'intermédiaire des amplificateurs 71 deux tensions de signes opposés et si la membrane 69 est suffisamment mince, les parties des céramiques placées sous les métallisations 61 et 67 vont, par exemple, se dilater et celles, placées sous les métallisations 63 et 65, vont se contracter, obligeant la partie centrale 13 à tourner légèrement, ce qui permettra de compenser les déformations de la partie extérieure 12 qui se seront produites sous l'effet des accélérations parallèles à l'axe de mesure 16 du gyrolaser.If the metallizations 61 and 67, 63 and 65 are connected together, if two voltages of opposite signs are applied to them via the amplifiers 71 and if the membrane 69 is sufficiently thin, the parts of the ceramics placed under the metallizations 61 and 67 will, for example, expand and those, placed under the metallizations 63 and 65, will contract, forcing the central part 13 to rotate slightly, which will make it possible to compensate for the deformations of the external part 12 which will have occurred under the effect of accelerations parallel to the measurement axis 16 of the laser gyro.

Il en sera de même avec les céramiques 62 et 68, 64 et 66, pour redresser les déformations de la partie extérieure 12 dans le plan du gyrolaser perpendiculaire à son axe de mesure.It will be the same with ceramics 62 and 68, 64 and 66, to straighten the deformations of the outer part 12 in the plane of the laser gyro perpendicular to its axis of measurement.

Pour la clarté du dessin, le branchement des métallisations 65 à 68 n'a pas été représenté et seules les métallisations 61, 63, 65 et 67 ont été représentées sur la vue en coupe du miroir mobile de la figure 13.For clarity of the drawing, the connection of metallizations 65 to 68 has not been shown and only the metallizations 61, 63, 65 and 67 have been shown in the sectional view of the movable mirror of FIG. 13.

Ainsi, en combinant, comme le montre le schéma de la figure 13, les différentes tensions, on peut réaliser à la fois les fonctions d'asservissement de la longueur de cavité, les fonctions d'asservissement du calage angulaire de la cavité optique et la correction des rotations parasites du miroir mobile piézoélectrique sous l'effet des diverses accélérations, de la même façon qu'avec le dispositif présenté dans les figures 8 et 10.Thus, by combining, as the diagram in FIG. 13 shows, the different voltages, it is possible to perform both the functions of servoing the length of the cavity, the servo functions of the angular setting of the optical cavity and the correction of parasitic rotations of the piezoelectric movable mirror under the effect of the various accelerations, in the same way as with the device presented in Figures 8 and 10.

L'asservissement de longueur de cavité 69 est réalisé de préférence selon un schéma bien connu de l'homme de l'art. Son signal de sortie 73 commande les huit métallisations par l'intermédiaire des 4 amplificateurs de tension 71 et 72. La voie de correction horizontale, identique à celle de la figure 10, reçoit sur ses entrées 49 et 48 les signaux d'accélération γ1 et les signaux de position de l'activation issus du détecteur 35.The servo length control 69 is preferably performed according to a scheme well known to those skilled in the art. Its output signal 73 controls the eight metallizations via the 4 voltage amplifiers 71 and 72. The horizontal correction channel, identical to that of FIG. 10, receives on its inputs 49 and 48 the acceleration signals γ1 and the activation position signals from the detector 35.

La voie de correction verticale, également idenntique à celle de la figure 10, reçoit, sur son entrée 38, le signal d'accélération γ2 et, sur l'amplificateur sommateur 47 le signal issu du circuit d'asservissement de l'alignement angulaire de la cavité 40.The vertical correction channel, also identical to that of FIG. 10, receives, on its input 38, the acceleration signal γ2 and, on the summing amplifier 47, the signal coming from the angular alignment control circuit of cavity 40.

Les deux circuits d'asservissement de longueur de cavité 62 et d'asservissement du réglage angulaire de la cavité 40 reçoivent sur leurs entrées, une tension représentant l'intensité lumineuse IL, mesurée par exemple par les cellules photoélectriques 7.The two cavity length servo-control circuits 62 and the angular adjustment servo-control circuit 40 receive on their inputs a voltage representing the light intensity I L , measured for example by photoelectric cells 7.

On pourra bien entendu utiliser toute autre configuration des céramiques du moteur piézoélecrrique de l'ensemble miroir piézoélectrique pour remplir simultanément les deux fonctions d'asservissement de longueur de cavité et de correction des rotations parasites sans sortir du cadre de l'invention.It is of course possible to use any other configuration of the ceramics of the piezoelectric motor of the piezoelectric mirror assembly to simultaneously fulfill the two functions of servo of cavity length and correction of parasitic rotations without departing from the scope of the invention.

Claims (10)

1. Device for eliminating the parasitic rotations of the mobile mirror or mirrors of a gyrolaser of the type comprising:
- an optical block (1) mounted for rotation on a support (25) and having at least one optical perimeter in the form of a closed loop, inside which two reverse laser waves are generated,
- means (6) and (7) for mixing these two waves so as to obtain a system of interference fringes on photoelectric, cells,
- mechanical activation means (8) and (9) for causing the optical block (1) to oscillate with respect to its support (25),
- at least one mobile mirror (10) having reflecting layers and driven for example by a piezoelectric motor (11), characterized in that the parasitic rotations of the mobile mirror (10), due to the deformations of the piezoelectric mirror assembly under the effect of the accelerations, are corrected by a piezoelectric means (26), creating a deformation equal to and opposite the initial deformation, controlled by an electric voltage coming from the activation system, which electric voltage is proportional to the accelerations undergone by said mobile mirror assembly.
2. Device according to claim 1, characterized in that the ceramics (26) preferably of semi-circular shape are bonded to the outside of the external part (12) of the piezoelectric mirror assembly.
3. Device according to claim 1, characterized in that the flat ceramics (28) are bonded to flat surfaces (27) formed on the external part (12) of the piezoelectric mirror assembly.
4. Device according to one of claims 1 or 2, characterized in that it comprises two pairs of ceramics (29) and (30) bonded to the periphery of the external part (12) of the piezoelectric mirror assembly, each acting in a direction for correcting all the deformations of said assembly.
5. Device according to one of claims 1, 2 or 3, characterized in that it comprises electric circuits for controlling the ceramics, which circuits are formed of:
- an adapter pre-amplifier (31) which receives a voltage from an activation position detector (35), preferably piezoelectric and a voltage from the acceleration information processing circuits and which represents the acceleration undergone by the gyrolaser in the direction parallel to the accelerations which the activation produces on the piezoelectric mirror,
- a gain and phase adjustment circuit (32),
- an inverter amplifier (33),
- two voltage amplifiers (34) which control the piezoelectric deformation correction ceramics.
6. Device according to one of claims 1 or 4, characterized in that it comprises two sets of electronic circuits, the first comprises an adapter amplifier (39), a gain and phase adjustment circuit (32), a phase-shift amplifier (33) and two voltage amplifiers (34), the device receives a voltage from an activation position detector, preferably piezoelectric and a voltage from the acceleration information processing circuits and which represents the acceleration undergone by the gyrolaser in the direction parallel to the accelerations which the activation on the mirror produces. The voltage leaving the voltage amplifiers controls the piezoelectric ceramics (30) for correcting the deformations in this direction. The second electronic circuit also comprises an adapter amplifier (39), a gain and phase adjustment circuit (32), an additional summator amplifier (47), a phase-shift amplifier (33) and two voltage amplifiers (34). It receives a voltage from the acceleration information processing circuits which represents the acceleration undergone by the gyrolaser in the direction parallel to its measurement axis as well as a voltage from a servo-control circuit controlling the angular adjustment of the optical cavity formed of an oscillator (41) a preamplifier (42), a demodulator (44), a corrector network (45) and an adapter amplifier (46). The pre-amplifier (42) of this circuit receives the light intensity information coming from the photoelectric cells (7). The voltage from the voltage amplifiers (34) controls the piezoelectric ceramics (29) correcting the deformations in a direction parallel to the axis of measurement of the gyrolaser.
7. Device according to one of claims 1, 2 or 4, characterized in that the correction ceramics comprise strip metallizations parallel to the axis of the piezoelectric mirror so that some strips (53) serve for detecting the stresses undergone by the ceramics because of the deformations of the external part (12) and the other strips (54) receive voltages from the voltage amplifiers (34). The associated electronic circuits comprise adapter pre-amplifiers (56) whose differential inputs receive the signals from the detecting strips (53) and also receive, along the axes, correction information coming either from the accelerations, or from a servo-control of the angular adjustment of the cavity. They also comprise corrector networks (55) for the stability of the servo-control, phase-shift amplifiers and voltage amplifiers (34).
8. Device according to claims 9 and 11, characterized in that the ceramics (60) of the electric voltage motor of the mobile mirror control both the movement necessary for cavity length servo-control and rotation correction which compensates for the deformation of the piezoelectric mirror assembly under the effect of the accelerations.
9. Device according to claim 8, characterized in that the piezoelectric motor is formed by ceramics (60), in the form of discs, bonded on each side of the external membrane (69), and one of the metallizations of which is divided into four sectors which receive a combination of the voltages for the cavity length servo-control, cavity angular adjustment servo-control, accelerations undergone by the gyrolaser and the angular position of the activation.
10. Device according to one of the preceding claims, characterized in that it applies to any laser with mobile mirrors subjected to resonance vibrations and particularly to any gyrolaser.
EP19880901867 1987-02-18 1988-02-18 Device for eliminating parasitic rotations of mobile mirrors in laser gyrometers Expired - Lifetime EP0312552B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8702091A FR2611039B1 (en) 1987-02-18 1987-02-18 LASER GYROMETER, DEVICE FOR SUPPRESSING PARASITIC ROTATIONS FROM MOBILE MIRRORS
FR8702091 1987-02-18

Publications (2)

Publication Number Publication Date
EP0312552A1 EP0312552A1 (en) 1989-04-26
EP0312552B1 true EP0312552B1 (en) 1991-05-29

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EP19880901867 Expired - Lifetime EP0312552B1 (en) 1987-02-18 1988-02-18 Device for eliminating parasitic rotations of mobile mirrors in laser gyrometers

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EP (1) EP0312552B1 (en)
FR (1) FR2611039B1 (en)
WO (1) WO1988006276A2 (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9651379B2 (en) 2014-11-17 2017-05-16 Honeywell International Inc. Eliminating ring laser gyro backscatter
CN115406432A (en) * 2022-11-01 2022-11-29 天津集智航宇科技有限公司 Vertical deformation compensation device and compensation method for laser gyroscope
CN115406428A (en) * 2022-11-01 2022-11-29 天津集智航宇科技有限公司 Laser gyro sensitive axial deviation open-loop control device and method under acceleration environment

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Publication number Priority date Publication date Assignee Title
EP0194301A1 (en) * 1984-09-14 1986-09-17 Honeywell Inc. Stable path length control elements

Also Published As

Publication number Publication date
WO1988006276A2 (en) 1988-08-25
FR2611039A1 (en) 1988-08-19
FR2611039B1 (en) 1990-01-05
WO1988006276A3 (en) 1988-12-29
EP0312552A1 (en) 1989-04-26

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